What is PPPoE?
Point-to-Point Protocol over Ethernet (PPPoE) is a network protocol which encapsulates PPP frames inside Ethernet. With PPPoE, multiple hosts in an Ethernet LAN are connected to the Provider Network and throughout this network, they connect Internet. Here, this connection is done over DSL and users share this DSL connection. By doing this, Point-to-Point Protocol over Ethernet provides a secure connection by establishing Point to Point connection over Ethernet technology. Connecting many users to their network over PPPoE technology is very useful and cost effective for Providers.
Point-to-Point Protocol over Ethernet is a Client / Server protocol. For the operation of Point-to-Point Protocol over Ethernet, firstly a Session must be established between PPPoE Client and PPPoE Server.
In this connection, the devices in the LAN are connected to PPPoE Client. This client is the Local Router of the user in a home network or in enterprise network. It is connected to Provider router network via DSLAM. Here, the Provider router is PPPoE Server. Throughout the Provider Router, Clients reach Internet.
PPPoE Session Establishment Stages
Point-to-Point Protocol over Ethernet has three stages. These Stages are :
1. Discovery Stage
2. Session Stage
3. Termination Stage
Let’s check these stage one by one.
PPPoE Discovery Stage
The first Stage, the Discovery stage, is the stage in which the PPPoE Client discovers the availabile PPPoE Servers, their MACs and determine one of them to establish a PPPoE session.
In PPPoE Discovery stage there are four messages. These messages are orderly given below:
PADI is the initialization message sent by the Client as broadcast to discover if are there any Server.
PADO is the answer of the Servers available as unicast to the requested Client.
PADR is the selection message of Client. This message is sent to the selected Server.
PADS is the set up message sent by Server. Session ID is sent in this last stage and the Session is established.